1. Technical Field
The present invention relates to an air conditioning system. More specifically, the present invention relates to an air conditioning system with an energy recovery device that extracts work from expanding refrigerant moving from a high-pressure zone to a lower pressure zone of the air conditioning system.
2. Background Information
Vehicle air conditioning systems utilize the phase changes of refrigerant fluids in order to extract heat from circulated air, and thus cool the air. A typical vehicle air conditioning system includes a compressor, a condenser, an expansion valve and an evaporator. The compressor compresses a cool vapor-phase refrigerant (e.g., Freon, R134a) to heat the same, resulting in a hot, high-pressure vapor-phase refrigerant. This hot vapor-phase refrigerant runs through a condenser, typically a coil that dissipates heat. The condenser condenses the hot vapor-phase refrigerant into liquid refrigerant. The liquid refrigerant is regulated through the expansion valve, which evaporates the refrigerant to a cold, low-pressure saturated liquid-vapor-phase refrigerant. This cold saturated liquid-vapor-phase refrigerant runs through the evaporator, typically a coil that absorbs heat from the air fed to the passenger compartment.
Basically, the input energy for a vehicle air conditioning system is typically represented by the power required to operate the compressor that compresses refrigerant vapor. Much of the energy added to the system through the compression process is expelled as kinetic energy during the expansion phase when the pressure of the refrigerant rapidly drops. In order to increase the efficiency of refrigeration systems, attempts have been made to recover some of the energy released during the expansion process and to convert the recovered energy into useful work. For example, one proposal to improve energy efficiency of a vehicle air conditioning system is disclosed in U.S. Pat. No. 6,272,871. Generally, in this patent, the air conditioning system is provided with an energy recovery device that recovers energy generated during operation of the air conditioning system. Specifically, the air conditioning system utilizes a vane-type expander (similar to a vane type compressor, but operating in reverse) to extract energy from normal operation of the air conditioning system. In this air conditioning system, the expanding refrigerant is used to rotate the vane-type expander that is connected to a shaft from which mechanical and/or electrical energy can be extracted.